/* Copyright (C) 2013-2021 TU Dortmund
 * This file is part of LearnLib, http://www.learnlib.de/.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package de.learnlib.oracle.equivalence.spa;

import java.util.Collection;
import java.util.stream.Stream;

import com.google.common.collect.Streams;
import de.learnlib.api.oracle.MembershipOracle;
import de.learnlib.oracle.equivalence.AbstractTestWordEQOracle;
import de.learnlib.oracle.equivalence.WMethodEQOracle;
import net.automatalib.automata.fsa.DFA;
import net.automatalib.automata.spa.SPA;
import net.automatalib.util.automata.conformance.SPATestsIterator;
import net.automatalib.util.automata.conformance.WMethodTestsIterator;
import net.automatalib.words.SPAAlphabet;
import net.automatalib.words.Word;

/**
 * An {@link SPA} version of {@link WMethodEQOracle} which generates test sequences based on the W-method for each
 * procedure.
 *
 * @param <I>
 *         input symbol type
 *
 * @author frohme
 */
public class WMethodSPAEQOracle<I> extends AbstractTestWordEQOracle<SPA<?, I>, I, Boolean> {

    private final int lookahead;
    private final int expectedSize;

    /**
     * Constructor. Convenience method for {@link #WMethodSPAEQOracle(MembershipOracle, int, int)} that sets {@code
     * expectedSize} to 0.
     *
     * @param sulOracle
     *         interface to the system under learning
     * @param lookahead
     *         the maximum length of the "middle" part of the test cases
     */
    public WMethodSPAEQOracle(MembershipOracle<I, Boolean> sulOracle, int lookahead) {
        this(sulOracle, lookahead, 0);
    }

    /**
     * Constructor. Convenience method for {@link #WMethodSPAEQOracle(MembershipOracle, int, int, int)} that sets {@code
     * batchSize} to 1.
     *
     * @param sulOracle
     *         interface to the system under learning
     * @param lookahead
     *         the (minimal) maximum length of the "middle" part of the test cases
     * @param expectedSize
     *         the expected size of the system under learning
     */
    public WMethodSPAEQOracle(MembershipOracle<I, Boolean> sulOracle, int lookahead, int expectedSize) {
        this(sulOracle, lookahead, expectedSize, 1);
    }

    /**
     * Constructor. Uses {@link Math#max(int, int) Math.max}{@code (lookahead, expectedSize - }{@link DFA#size()
     * hypothesis.size()}{@code )} (for each procedural {@code hypothesis}) to determine the maximum length of
     * sequences, that should be appended to the transition-cover part of the test sequence to account for the fact that
     * the system under learning may have more states than the current hypothesis.
     *
     * @param sulOracle
     *         interface to the system under learning
     * @param lookahead
     *         the (minimal) maximum length of the "middle" part of the test cases
     * @param expectedSize
     *         the expected size of the system under learning
     * @param batchSize
     *         size of the batches sent to the membership oracle
     *
     * @see WMethodTestsIterator
     */
    public WMethodSPAEQOracle(MembershipOracle<I, Boolean> sulOracle, int lookahead, int expectedSize, int batchSize) {
        super(sulOracle, batchSize);
        this.lookahead = lookahead;
        this.expectedSize = expectedSize;
    }

    @Override
    protected Stream<Word<I>> generateTestWords(SPA<?, I> hypothesis, Collection<? extends I> inputs) {
        if (!(inputs instanceof SPAAlphabet)) {
            throw new IllegalArgumentException("Inputs are not an SPA alphabet");
        }

        @SuppressWarnings("unchecked")
        final SPAAlphabet<I> alphabet = (SPAAlphabet<I>) inputs;

        return Streams.stream(new SPATestsIterator<>(hypothesis,
                                                     alphabet,
                                                     (dfa, alph) -> new WMethodTestsIterator<>(dfa,
                                                                                               alph,
                                                                                               Math.max(lookahead,
                                                                                                        expectedSize -
                                                                                                        dfa.size()))));
    }
}